1. Field of the Invention
The present invention relates to apparatus and method for inhibiting decomposition of germane, and to semiconductor process systems including such apparatus and arranged to carry out such method.
2. Description of the Related Art
Germane (GeH4) is a highly reactive gas that is susceptible to spontaneous decomposition. Depending on the speed of the reaction, the spontaneous decomposition of germane can lead to deflagration (sub-sonic reaction) or explosion (supersonic reaction).
Spontaneous decomposition of germane in a sealed package, e.g., a closed vessel holding such gas, may lead to very rapid increase in pressure and temperature in the package. In extreme cases, runaway increases in pressure and temperature may occur, which exceed the corresponding thermal and baric limits of the package, resulting in bursting of the package and dispersion of germane into the ambient environment.
Random deflagration of germane is known to occur. In consequence, the packaging densities of germane are typically limited by the pressures that could be attained upon decomposition of the material. The decomposition reaction
GeH4(g)xe2x86x92Ge(s)+2H2(g)
indicates that the molar quantities of the product double the initial value (molar quantity of gas). This effect, combined with the exothermic character of the decomposition reaction, results in a rapid and substantial increase in pressure inside the vessel in deflagration as well as in explosion events.
The foregoing decomposition susceptibility of germane has greatly limited the commercial application of this gas. While germane is very useful in semiconductor manufacturing as a source reagent for germanium (Ge), e.g., as a dopant or bulk component in semiconductor films and materials, the risk of fire and explosion attendant its use have caused other, less suitable Ge source reagents to be employed, or alternatively, double-containment vessels, flame arrestor systems and other safety equipment must be employed to ensure that the risk of spontaneous decomposition does not jeopardize the semiconductor manufacturing facility and its operating personnel.
It would therefore be a substantial advance in the art to provide an apparatus and method for the use of germane gas that avoids the aforementioned deficiencies of the prior art.
The present invention relates generally to apparatus and method for providing germane in a manner that substantially reduces the risk and consequences of spontaneous decomposition of germane gas.
In an apparatus aspect, the invention relates to a germane storage and delivery system, including:
a gas storage and dispensing vessel having an enclosed interior volume;
activated carbon sorbent medium in the interior volume of said gas storage and dispensing vessel;
germane gas in said gas storage and dispensing vessel, said germane gas comprising germane gas adsorbed on said sorbent medium in said interior volume and free germane gas present in said interior volume in a non-adsorbed state;
means for desorbing germane from said sorbent medium and dispensing same from the vessel;
wherein the activated carbon sorbent medium is deflagration-resistant in relation to the germane gas adsorbed thereon, under conditions in which said free germane gas in said interior volume in a non-adsorbed state undergoes deflagration.
In a method aspect, the invention relates to a germane storage and dispensing method comprising:
physically adsorbing germane gas on an activated carbon sorbent medium in a containment zone also comprising free germane gas in a non-adsorbed state;
selectively desorbing germane from said activated carbon sorbent medium and discharging same from the containment zone;
wherein the activated carbon sorbent medium is deflagration-resistant in relation to the germane gas adsorbed thereon, under conditions in which said free germane gas in said containment zone in a non-adsorbed state undergoes deflagration.
The deflagration-resistance of the activated carbon sorbent medium and the conditions under which free germane gas in the interior volume of the gas storage and dispensing vessel undergoes deflagration, is measured at a temperature of 65xc2x0 C. and a pressure of 650 torr.
In a further aspect, the invention relates to a method of preparing an activated carbon sorbent material for use, such method comprising:
purging the sorbent material with inert gas;
evacuating the inert gas from the sorbent material;
heating the sorbent material under vacuum to elevated temperature, and maintaining such vacuum and elevated temperature for sufficient time to dehydrate the sorbent material;
cooling the sorbent material under vacuum to ambient temperature;
passivating the sorbent material with a sorbate gas to which the sorbent material has sorptive affinity, at elevated temperature;
removing sorbate gas from the sorbent material; and
cooling the sorbent material under vacuum to ambient temperature.
Other aspects, features and advantages of the invention will be more fully apparent from the ensuing disclosure and appended claims.